The embodiments relate to a new method and apparatus for a belt tensioner.
Many automobile engines currently on the market utilize an endless power transmission belt for driving a plurality of driven accessories. They employ a tensioning system utilized to provide a tensioning force on the endless power transmission belt, which may be of any suitable type known in the art. Preferably, the belt is made primarily of a polymeric. KEVLAR or Aramid material because the unique features of the tensioner of this invention readily permit the tensioner to tension a belt having a polyester load-carrying cord in an efficient manner.
In many of these automotive accessory drives it is necessary to provide a correct tension to control a tension ratio throughout the life of the belt. With the advent of the single belt V-ribbed drive system, this is of increasing importance since belts are longer and some accessories are driven off the backside of the belt as a flat belt drive. Automatic tensioners of various descriptions have been developed having the requisite characteristics enabling them to tune the belt system to remove input torsionals and prevent or reduce harmonics, while allowing the tensioner to respond to changes in the belt tension requirements. For instance, see U.S. Pat. Nos. 4,596,538, 4,832,666, and 5,443,424 to Henderson, U.S. Pat. Nos. 4,938,734, 5,030,172 and 5,035,679 to Green, et. al., U.S. Pat. No. 5,190,502 to Gardner, et. al., or U.S. Pat. No. 5,348,514 to Foley, all now incorporated into this application by this reference thereto.
A section of prior art tensioners, as seen in FIGS. 7-8, includes a bushing 100 with a tapered outer diameter 102, a straight inner diameter 104, and a flat flange 106. Use of this bushing 100 results a large gap 108 between a hub section 110 of a support 112 and an arm 114. A problem exists because any axial movement of the bushing 100 will either increase or decrease clearance in the gap 108 between the bushing 100 and the arm 114. Ideally, the clearance in the gap 108 between the bushing 100 and the arm 114 should be zero because minimizing this clearance in the gap 108 is one of the ways to control alignment of the arm 114. However, zero clearance can lead to the arm 114 freezing on the hub 110, thus some clearance is needed. If alignment is not controlled, the tensioner can become unstable and the belt can slip off the tensioner pulley. If this happens, the belt can vibrate and jump off other pulleys in the engine, which can cause the engine to stop functioning. This prior art bushing may also include grooves 131 on either or both of an outside surface (not shown) and inside surface 133B to hold and distribute grease or lubricants.
Several embodiments provide a tensioner for a power transmission belt that operates on an endless path. The tensioner comprises an arm comprising a belt engaging section and a drum section, a support member for securing the tensioner relative to the belt, the arm pivoting about the support member, and a spring that urges the arm to pivot about the support member in a first direction and urges the belt engaging section against the belt with a force to tension the belt. The tensioner further comprises a cavity between the arm and the support member and a bushing comprising a bowed flange positioned in the cavity.
Another aspect is to provide a bushing with a straight inner diameter and a tapered outer diameter. Another aspect is to provide a bushing with an inner surface comprising a fixed diameter and an tapered outer surface.
Another aspect is to provide a bushing with a flange comprising cutout sections.
Another aspect is to provide a bushing whose bowed flange biases the bushing against the arm. Another aspect is to provide a bushing whose bowed flange biases the bushing along its longitudinal axis.
Another aspect is to provide a housing for the spring in the tensioner.
Another aspect is to provide a hub on the support member about which the arm pivots.
Another aspect is to provide a new method for utilizing a belt tensioner, the method of having one or more of the novel features as set forth above or hereinafter shown or described.
Several embodiments provide a method of utilizing a tensioner for a power transmission belt that operates on an endless path. The method comprises the steps of providing an arm comprising a belt engaging section and a drum section, providing a support member for securing the tensioner relative to the belt, the arm pivoting about the support member, and providing a spring that urges the arm to pivot about the support member in a first direction and urges the belt engaging section against the belt with a force to tension the belt. The method comprises the further steps of providing a cavity between the arm and the support member and providing a bushing comprising a bowed flange positioned in the cavity.
Other objects, uses, and advantages are apparent from a reading of this description, which proceeds with references to the accompanying drawings form a part thereof and wherein: